Somtimes when fish develop white spots its not ich. When water quality, temp, or other factors stress fish, they become vulnerable to bacteria and fungus.
If it is ich, then best course is to remove fish to a quarentine tank and treat with methelene blue for 2weeks at 30°c. The empty tank will be clear of ich if you leave the heat on and have no fish in it for two weeks. I would add salt to the empty tank to clear out any and all fungus or parasites.

Try daily water changes for a couple days first to see if your white spots are maybe not ich but fungus or parasites. In good clean water most fish can shrug off fungus and bacteria, but in poor water quality they get sick easier.

Fourth day of Ich
Temperature up at 80 degrees, first three doses of treatment added, one more to go on Saturday and 10 more days of high temp.

Fish looking much better only one or two spots left on one or two fish. Fish are loving the heat, flying round the tank. When Ich has gone as long as string algae stays away I will only lower the temp slightly. In fact I even thought of adding a second heater on a timer, setting one heater at 23 degrees and one at 27 degrees. The one set on the higher heat would be on timer and would come on with the light to try and recreate the heat of the sun. Idle brain has stooped thoughts at times.

Today I was going to do a 20% water change but I'm on night shift and slept to long. However water has good numbers. Will try to do it tomorrow sleep permitting.

Last dose of treatment added. I would however advise anybody buying treatment read the bottle themselves and not trust totally the LFS. I told the chap exactly what I had in my tank and he advised a certain treatment. Looking at the label it states do not add if you have shrimp or snails of which I have both. Not happy is the word for today. On the other hand I may be lucky as they don't seem affected by it, yet. Big piece of learning there ALWAYS READ THE LABEL ON MEDICATION